The culmination of the Navy's annual training maneuvers, they were unscripted, free play exercises involving large concentrations of ships, airplanes, and troops.

[5] Modern shipbuilding began in 1882, replacing the largely decrepit wooden-hulled ships built during and after the Civil War with new, steel-hulled vessels, beginning with USS Dolphin.

[15]Fleet Problems II, III, and IV all represented different phases of the same scenario, exploring the initial moves in a notional war against Japan, and took place within the same two months of 1924.

This portion of the exercise also aimed to practice amphibious landing techniques and transiting a fleet rapidly through the Panama Canal from the Pacific side.

He learned the Blue Fleet's schedule of passage through the Canal from locals, and prepared to board USS California (BB-44), but turned back when he spotted classmates from the United States Naval Academy - who would have recognized and questioned him - on deck.

The Black Force, the aggressor, was formed from the United States Battle Fleet, including the US' first aircraft carrier, USS Langley (CV-1), along with two seaplane tenders.

[28] Both fleets failed to observe radio silence, allowing their opponents to collect transmissions, perform cryptanalysis, and in Black's case, to break Blue's codes.

A series of other contested amphibious landings followed, and by the time the exercise ended on 27 April 1925, almost 30,000 Marines (most fictional, represented by smaller units) were advancing on Scofield Barracks, well into the interior of Oahu.

Army and Navy leadership widely agreed on the need to improve Hawaii's defenses, increasing the size of the garrison and expanding aircraft bases.

It was designed to test a discrete portion of War Plan Orange: the ability of an American naval force to relieve an Army garrison under siege in Manila.

Fleet Problem VI was notable in being the first exercise to include an aircraft carrier within a circular defensive formation, pioneering a practice that became commonplace in World War II.

It focused on the same tasks of convoy defense and relief of a besieged garrison as Fleet Problem VI, and again used the Panama Canal as a stand-in for Manila.

[11] These forces represented a significant commitment of the total US Navy: 72% of the fleet's battleships, 68% of the destroyers, and 52% of modern combat aircraft were involved in the scenario.

[38] This time, however, Saratoga and Langley were "disabled" by a surprise attack from Lexington, showing how quickly air power could swing the balance in a naval action.

Black, attacking from the west, was to land forces and establish bases in Central America and destroy the Panama Canal, while Blue defended with an aviation-heavy fleet.

Blue, based in Hawaii, was to sail east and invade three "enemy" ports on the North American Pacific coastline to try to gain a foothold for future operations.

[41] After-action critiques stressed the growing importance of naval aviation, and an increased need for the construction of aircraft carriers in the event of a war in the Pacific.

[41] Held 10–17 February 1933, Fleet Problem XIV was the first naval exercise to test simulated aircraft carrier attacks against the west coast of the United States.

Pacific cities had for decades vied for permanent stationing of U.S. military assets, and vulnerabilities exposed through the exercises were used by metropolitan navy boosters to leverage their cases.

[44] Held in May 1934 in Hawaii, this was a three-phase exercise which encompassed an attack upon and defense of the Panama Canal, the capture of advanced bases, and a major fleet engagement.

[46][48] This exercise was held in May 1937 in Alaskan waters and in the vicinity of the Hawaiian Islands and Midway, practicing the tactics of seizing advanced base sites—a technique later to be polished to a high degree into close support and amphibious warfare doctrines.

Over 60 warships, including the aircraft carrier USS Ranger (CV-4), were engaged in these Atlantic patrols at the time of Fleet Problem XXI, which ran from 1 April to 17 May 1940, shrinking the wargame.

[53] Fleet Problem XXI was preceded in March with a mobilization exercise, where a simulated period of rising tension allowed the US Navy to practice distribution of secret orders, personnel recall, contingency planning, and other aspects of pre-war crisis.

[54] Despite the war in Europe, President Roosevelt suggested to CNO (Chief of Naval Operations) Harold Stark that the 1940 fleet problem focus on the southwest Pacific.

The American fleet, under the command of Admiral Adolphus Andrews, was ordered to prevent the seizure of an advanced base in the Hawaiian islands by the enemy force.

[citation needed] There were four proposals for the Fleet Problem scheduled for 1941, with hypothetical exercise areas in the Marshall Islands, Panama, the coast of Mexico, and the Northeastern Pacific.

Reporter Leland Speers described how, due to international tensions, the fleet would remain concentrated in Pearl Harbor and was engaging in "practically continuous" gunnery training.

[57][58] The fleet would remain in and around Pearl Harbor until raided by Japanese air forces on 7 December 1941, which prompted the United States' entry into World War II.

Later in 2018, Carrier Strike Group Nine participated in a Fleet Problem involving a contested transit from San Diego to Hawaii, which Rear Admiral Steve Koehler described as "a complete free-play high-end event.

"[60] In 2021, an unnumbered Fleet Problem included a large number of unmanned vehicles led from USS Michael Monsoor (DDG 1001), a Zumwalt-class destroyer.